The production of heteroantibodies for targeting effector cells comprising an antibody specific for the high affinity FcRI receptor linked to a second antibody specific for an antigen present on a target cell has been described. See, for example, Segal et al., U.S. Pat. No. 4,676,980; and Karpovsky et al., J. Exp. Med. 160:1686-1701 (1984). Such constructs can be used to specifically kill unwanted cells (e.g. tumor cells or virus infected cells).
Recently, a monoclonal antibody has been produced which reacts with the high affinity Fc-gamma receptor through its variable region. Serum immunoglobulin does not compete with the antibody for binding to the Fc receptor. See, for example, Application; Anderson et al., J. Biol. Chem. 261:12856 (1986); and Shen et al, J. Immunol. 137:3378-3382 (1986). Consequently, serum IgG does not interfere with targeted effector cell killing.